docker.md

• Docker
• Flow
  • Basic
  • With volumes and network
• Docker Compose
  • Example docker-compose.yaml
• CI/CD
• Language specific
• Run app in production

Docker

• containerizing of programs(running them in seperate processes) using linux namespaces and cgroups
• write Dockerfile in app root to build image using docker docker build
• may need different containers for app and DB.
• could mount db file as docker named volume into app
• docker can create network to talk to different containers on same network
  • app container talks to db container
• mangement of multiple containers by Container Orchestration Frameworks like Kubernetes

Flow

Basic

• write Dockerfile

 # syntax=docker/dockerfile:1
 FROM node:12-alpine
 RUN apk add --no-cache python g++ make
 WORKDIR /app
 COPY . .
 RUN yarn install --production
 CMD ["node", "src/index.js"]

• build using docker build -t app_docker .
  • -t => --tag
  • . => create build from current directory
• run your build using docker run -dp 3000:3000 app_docker
  • -d -> background mode
  • -p -> map container port to host port

With volumes and network

• volumes are data stores in filesystem and images can be built along with them.
  • (ex: db is stored in a different file, and want to use it as persistend db across builds)

Docker Compose

• create containers with services and volumes defined in a docker-compose.yaml file
• docker compose up automatically creates a network
• -d to run in background
• define services and volumes in the yaml
  • services may contain different app labels and define
    • image - image to to be used
    • command - optional commands
    • port - mapping of port of container to host
    • working_dir
    • volumes - named volumes(defined in top level volumes prop) or bound(as paths)
    • environment - various properties related to env vars.
• images can be fetched from docker hub node12:alpine, mysql:5.7

Example docker-compose.yaml

version:    "0.1"

servies:
    app:
        image:  django-app
        port:
            - 3000:3000
        working_dir:    /django-app
        volumes:
            -   ./:/app
        environment:
            MYSQL_HOST: mysql
            MYSQL_USER: root
            MYSQL_PASSWORD: password
            MYSQL_DB:   jarvis
    mysql:
        image:  mysql-app
        volumes:
            -   jarvis-app:/var/local/mysql
        environment:
            MYSQL_ROOT_PASSWORD:    password
            MYSQL_DATABASE: jarvis

volumes:
    jarvis-app:

CI/CD

Language specific

Run app in production